Screening drum for dewatering suspensions



2 Sheets-Sheet 1 I'll I Jan. 9, 1951 K. R. LINDBLAD SCREENING DRUM FOR DEWATERING SUSPENSIONS Filed Feb. 4, 1946 Jan. 9, 1951 K. R. LINDBLAD SCREENING DRUM FOR DEWATERING SUSPENSIONS 2 Sheets-Sheet 2 Filed Feb. 4, 1946 Patented Jan. 9, 1951 SCREENING DRUM FOR DEWATERING SUSPENSIONS Karl Roland Lindblad. Sundsbruk, Sweden, assignor to Svenska Cellulosa Aktiebolaget. Stockholm, Sweden, a joint-stock company of Sweden Application February 4, 1946, Serial No. 645,338 In Sweden January 22, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires January 22, 1964 Claims.

1 The present invention relates to a screening drum for dewatering or draining suspensions, particularly fibrous suspensions, the said drum being intended to rotate partially immersed in the suspension.

The drum consists of an outer shell provided with screening Openings and an inner shell without such openings. Between the said shells there are provided longitudinal partitions which divide the space between the shells into cells. These cells individually or in groups, comprising two or more cells, communicate with the interior of the drum by a duct which is recurved in the direction of rotation and has square or rectangular cross section. The said discharge ducts are placed close to one another in the axial direction, at one or both ends of the drum and run closely along the inner shell.

An embodiment of a drum according to the invention for concentration of fibrous suspensions is illustrated on the accompanying drawing, in which:

Fig. l is a longitudinal section, Fig. 2 is a transverse cross section on line II-II in Fig. 1, and Fig. 3 is fragmentary transverse section of a modified construction.

In the drawing the reference numeral! designates a trough into which the fibrous suspension fiows through a channel 2. In the trough there is immersed a rotatable screening drum on which the formed fibrous web is taken up. The said fibrous web is carried off from the upper part of the drum by means of a take off roller 3 or similar device. The water passing through the screening drum leaves at one end of the drum through an opening in the said end and is led off. The water in thedrum is held dammed up according to the drawing by a damming device 4; however, it is not necessary to dam,

up the water'but it may fiow out unrestrictedly. The screening drum consists of an outer perforated shell 5, on the outside of which there is fixed a wire screen, and of an inner unperiorated, partly conical shell 6. The space between the shells is divided by means of partitions 1 so that a number of longitudinal cells 8 are formed which receive and lead off the water which has passed through the perforated shell 5. Each cell is provided with a discharge duct 9. The discharge ducts are contiguous to the inside of the inner shell at its one end, the inner shell serving also as one wall of the ducts, and are arranged in such a way that they form a number of annular sections of square or rectangular cross section located beside each other in the axial direction of the drum. Three, four or more ducts may belong to each section according to the desired height of suction. It is not necessary that each cell is provided with an individual duct but the cells may be united to groups comprising two or more cells 8 having a discharge duct 9 common to each group. as illustrated in Fig. 3.

When the screening drum is rotating, each cell and each discharge duct will be successively filled with water due to the pressure difference existing between the outer and the inner liquid level, the drum being at the same time coated with a fibrous web. According as the discharge ducts are filled with water, water begins to flow off, which continues until the cell has reached its uppermost position at which the water should substantially have left the cell. Due to the suction action produced in the cell as soon as the cell arrives above the liquid level in the trough, an effective draining of the fibrous web formed on the outside of the drum is obtained. A simple and effective draining of the formed fibrous web iS obtained with a screenin drum according to the invention. Moreover, due to the shape and the arrangement of the discharge ducts, which is a characteristic feature of the invention, a valuable saving of material and a considerable simplification of the manufacture are obtained over known types of screening drums, particularly in view of the pos sibility of using ordinary sheet metal for the inner shell, whereby the shell can be welded together.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A screening drum for draining suspensions such as fibrous suspensions and intended to rotate in one direction While being partially immere-ed in a body of such suspension, said screening drum including in combination an outer generally cylindrical shell provided with screening openings, an inner imperforate shell spaced from said outer shell, a plurality of longitudinal partitions between the outer and inner shells dividing the space therebetween into a plurality of cells, discharge ducts communicating between said cells and the interior of the drum, said discharge ducts being contiguous to said inner shell, bent backwards in relation to the direction of rotation of the drum and grouped at one zone of the drum info a plurality of annular sections adiacently disposed in the axial direction of the drum with a plurality of ducts to each section, and said inner which the discharge ducts have rectangular cross 7 section.

- 5 3. A screening drum as claimed in claim 1, in

which thedischarge ducts are brought together at least at one end of the drum.

4. A screening drum according to claim 1, in which the cells individually communicate with the interior oi the drum by means or a discharge duct.

cells communicate with the interior of the drum is by means of a common discharge duct.

KARL ROLAND LINDBLAD.

, v nmlmcss cmm The following references are of record in the file 01 this patent:

UNITED s'ra'rms PATENTS Number Name Date 770,307 Parker Sept. 20, 1904 819,004 Couper Apr. 24, 1906 1,205,672 Seybold Nov. 21, 1916 10 1,816,132 Strindland July 28, 1931 2,362,300 Nyman Nov. 7, 1944 FOREIGN PATENTS Number Country Date 34,131 Sweden Jan. 2, 1913 78,737 Sweden Oct. 24, 1933 233,316 Germany Apr. 4, 1911 260,875 Germany June 10, 1913 457,832 Great Britain Dec. 7, 1936 510,034 Great Britain July 26, 1939 

